Circuit breakers having improved tripping mechanisms



Sept. 28, 1965 H. s. WINGARD 3,209,093

CIRCUIT BREAKERS HAVING IMPROVED TRIPPING MECHANISMS 2 Sheets-Sheet 1 Filed May 21, 1962 FIG. I

INVENTOR. BY HENRY s. wmemo ATTORNEY CIRCUIT BREAKERS HAVING IMPROVED TRIPPING MECHANISMS Filed May 21, 1962 Sept. 28, 1965 H. s. WINGARD 2 Sheets- Sheet 2 FIG.5

INVENTOR HENRY S. WINGARD QZML. PM;

ATTORNEY United States Patent Oflice 3,209,098 Patented Sept. 28, 1965 3,209,098 CIRCUIT BREAKERS HAVING MPROVED TRIPPING MECHANISMS Henry S. Wingard, Cranford, N.J., assignor to Federal Pacific Electric Company, a corporation of Delaware Filed May 21, 1962, Ser. No. 196,094 18 Claims. (Cl. 200-88) This invention relates to circuit breakers and more particularly to circuit breakers having trip mechanisms which operate to trip the breaker instantaneously on overloads above a given level and after suitable time delay on lesser overloads.

'An object of this invention is to provide an improved magnetic trip mechanism incorporating means for adjusting the minimum value of current at which said trip mechanism will operate instantaneously.

Another object of this invention is to provide an electromagnetic trip mechanism which incorporates an armature having a pole-face bridging element and which device utilizes a portion of the armature to provide a hold-back force thereby restraining the armature until the desired operating level of overcurrent is reached.

Yet another object of the invention is to provide an improved trip mechanism which allows the overtravel of the time delay element beyond the trip point of the breaker without disturbing the preset calibration of said element.

Still another object of this invention is to provide a molded case circuit breaker having an improved latching arrangement.

A further object of the invention is to increase the ac curacy of the relative positions of the associated mechanism of a circuit breaker and ,to thereby reduce breakerto-breaker variations in characteristics.

Yet another object of the invention is to increase the control of the extent of latch engagement in molded case multipole circuit breakers having asingle operating mechanism.

. Further features of the invention and its other aspects and advantages will become clear from the following detailed disclosure taken with an illustrative embodiment shown in the accompanying drawings. In those drawings:

FIG. 1 is a side view of a multipole circuit breaker embodying the invention partly in section as viewed from the plane 11 in FIG. 2;

FIG. 2 is a plan view of the circuit breaker of FIG. 1 with some parts broken away and other parts omitted;

FIG. 3 is a perspective view of the instantaneous trip mechanism showing the thermally actuated time delay element;

FIG. 4 is a fragmentary cross-sectional view of the common trip bar taken along the plane 4-4 of FIG. 2; and

FIG. 5 is a fragmentary crosssectional view of the trip bar and latch on an enlarged scale, as viewed from the plane 55 of FIG. 2 with some parts omitted and with other parts broken away or in section in the interest of clarity.

Referring to the drawings, the circuit breaker mechanism is enclosed in a case of molded insulation including a cover and a base 12. The circiut through an illustrative pole of the circuit breaker (when it is closed) .extends from one terminal 14 to the stationary contact 16, thence to movable contact 18, through the contact arm 20, along conductive flexiblebraid 22 through bimetal 24 to conductive bar 26, and thence to the opposite terminal 28. Contact arm 20, which carries contact 18, is in turn carried by pivot 30 inthe contact arm carrier 32 and is biased by compression springs 34 in the direction to build up contact pressure when the contacts are closed. When the contacts are open, the swing, of the contact arm 20 produced by the spring 34 is limited by the engagement of the portion 20a of the contact arm with the bottom edge 32a of the channeled shaped contact arm carrier 32. The contact arm carrier 32 is afiixed to the insulated shaft 36 the ends of which are pivotally supported by corresponding bearing portions of the molded base 12. Plural contact arm carriers 32, with respective contact arms 20, are mounted on the aforesaid shaft for coordinated cooperation of the contacts of a multipole circuit breaker.

An over-centering spring mechanism indicated generally at 38 is provided for operating the contacts between the closed and open positions and for effecting automatic release in opening of the contacts in response to an overload. The operating mechanism includes a manual operating lever 40 and handle 42. Lever 40 is pivoted at its lower extremity in a fixed frame 44 secured to the breaker base 12. The frame includes a pair of spaced metal members or plates which extend from a point adjacent the midpoint of the breaker casing toward one end of the case. An overload release members or cradle 46 has a pivot 48 fixed in the frame 44. A pair of toggle links 50, 52 are pivotally connected to each other at pin 54 which is the knee of the toggle (FIG. 1). These toggle links have a top pivot 56 and a bottom pivot 58 in members 46 and 32 in the center pole of the illustrative breaker. Where there are plural contact carriers 32, for a corre sponding number of poles, there is here (as is usual) only a single operating mechanism for all of the contact arm carriers operated by the square shaft 36. Two pairs of springs 60 extend between the manual lever 40 and the knee 54 of the toggle although only one pair is visible in FIG. ,1.

The breaker operating mechanism 38 and a cooperating secondary latch 61 are located at the center pole posi tion of the described embodiment of the invention. The end 47 of the cradle 46 remote from pivot 48 is normally restrained against movement in the toggle-collapsing direction by secondary latch 61. Secondary latch ,61 has a back wall 62 which is pivoted at two spaced points 63 on the frame 44. Latch arm 64 extend at right angles to the back wall 62. An offset portion 65 of the latch wall 62 is engaged by end 47 of the cradle. The point of engagement between the cradle and secondary latch is almost in line with the pivots 63 so as to produce a force having a minimal component tending to rotate the latch about its pivot. The maximum component of force is directed vertically (FIG. 5) through the pivot 63 and is taken up by the frame 44. A rearwardly extending projection or tail 66 depends from the latch wall 62 and cooperates with the cradle end 47 during the latch-resetting operation. Latch stop 68 engages the frame 44 to limit the rotation of thesecondary latch in the trip direction.

In FIG. 2 the trip bar 70, of insulation, extends across all the pole positions and is pivoted at two points 71 on the frame 44. Spring 72 is tensioned between the trip bar 70 and the latch 61 and urges them into engagement as shown in FIG. 5. Spring 72 engages the trip bar 70 at a point adjacent to and slightly above its pivotal axis (71, 71) to provide counterclockwise bias and engages the latch wall 62 at a point spaced above the latch pivotal axis 63, 63 to bias the latch 61 clockwise, toward latch surface 75.

Referring to FIG. 5 the secondary latch arm 64 has a flat-surface right-angle portion 74 which engages the upper surface 75 and end 76 of a relatively stiff metal primary latch 77. Surface 75 is part of the rolled surface of the metal and is smooth. Edge 76 is burr-free, having been sheared downward. Main latch 77 is secured at its .opposite end to the trip bar 70 as by rivets 78. The amount of secondary to primary latch engagement is determined by the configuration In the embodiment shown in the drawings the end 76 of the primary latch 77 engages the vertical surface of the secondary latch arm end 74 to limit their inward movement toward one another. The point of engagement of the secondary latch arm 64 and the primary latch 77 is a reaction point for the previously described small component of force exerted by the cradle end 47 which tends to rotate the secondary latch 61 clockwise about its pivotal axis 63, 63, as viewed in FIG. 5. The configurations of the secondary latch portion 74 and latch surface 75 produces a force on the primary latch 77 which is in a vertical plane close to the trip bar pivot 71, 71 and to the left of the pivot as viewed in FIG. 5. The major com ponent of this force acts through the pivot 71, 71. The selected configuration produces a small counterclockwise moment that biases the trip bar 70 toward the secondary latch. The forces and spacings associated therewith result in relatively low forces between the primary latch 77 and secondary latch 61. This arrangement of'secondary latch 61, primary latch77 and spring 72 represents a distinct improvement over comparable latching mechanisms in such circuit breakers. Primary latch 77 is spaced from and substantially parallel to the rear face of the trip bar 70. The end 76 of primary latch 77 passes through a trip ba'r notch 82 toward the secondary latch 61. Where ambienttemperature compensation is desired the primary latch 77 may be made of bimetallic material having a desired rate of deflection in response to temperature change.

The relative locations of the pivots of the trip bar, that carries the main latch 77, and the secondary latch 61 are fixed by the pivots of those parts in the frame 44. The pivoting of the trip bar 70 of a multi-pole circuit 'breaker on the frame 44 that carries the single operating toggle is an improvement over previous construction wherein the trip bar has been carried by themolded case. Easier assembly and control of the extent of latch engagement 74, 75 is realized.

Each of the poles is provided with an overcurrent sensing means indicated generally at 80. Since they are identical only one such sensing means will be described. The overcurrent sensing means 80 is provided with portions which respond to different overc'urrent levels. For sustained overloads it is desirable that the overcurrent sensing means 80 incorporate an inverse time characteristic so that as the overload current increases the time of response is decreased. This mode of operation is obtained by employing the known characteristics of himetal member 24 through which the current flows when the breaker is closed. B-imetal 24 deflects, due to overload current, and engages an adjustment screw 84 carried by trip bar 70. Continued deflection of the bimetal drives the trip bar 70 counterclockwise, to disengage the secondary latch 61 from the primary latch 77 and open the breaker as will be explained below.

' In order to obtain the desired instantaneous trip of the circuit breaker upon the occurrence of severe overloads a stnucture which responds electromagnetically to the current flow through the bimetal 24 is provided. Referring to FIG. 3 a channel or U-shaped pole piece 86 fabricated from ferromagnetic material is positioned about and spaced from the bimetal 24 and is secured at one end to the conductive bar 26 to which the bimetal 24 is also secured. The bight portion or web 88 is normally substantially parallel to the broad face of bimetal 24 and a pair of legs 90 extend perpendicularly therefrom. The length of the legs 90, measured from the web 88, increases from a point adjacent the fixed end of the bimetal 24 to the point where an armature supporting arm 92 projects from each of the legs. The length of the legs 90 remains constant from arm 92 to the free end of the pole piece 86. The end surfaces of the legs 90 lie in the same plane and form pole faces 94. Each arm 92 has an upwardly directed end projection 96. The arms may be of the confronting pai'tsa {considered as dividing each pole face 94 into upper and lower sections, 9411 and 94b respectively.

An armature 98 is carried by the arms 92. Armature 98 is fabricated from ferromagnetic material and is wide enough to span across and electromagnetically bridge the pole faces 94 of the legs 90. The armature is notched at 100 to provide clearance for the arms 92 which position and support the armature on the pole piece. Armature 98 is bent adjacent the notches 100 to form an upper armature portion 98a in one plane and a lower armature portion 98b in an intersecting plane inclined thereto. The line of intersection of the plane of the upper and lower armatures 98a, 98b is the pivot 99 for the armature on the pole piece 86. Upper armature 98a is made con siderably shorter than lower armature 98b for reasons which will be explained later. The upper armature 98a has an extension 101 which projects, at an angle to the plane of the upper armature 98a, toward the trip bar 70. The armature 98 is resiliently biased by a U-shaped spring 102 so that the upper segment 98a is urged against the upper pole faces 94a of the pole piece 86, thereby providing a considerable gap between the lower armature 98b and its cooperating pol-e faces 94b. The spring 102 also retains the armature 98 on the arms 92 and against the pole piece 86. It should be noted that the armature is pivotally mounted on the pole piece and at all times bridges the pole faces 94. The inclination of the lower pole faces 94b toward the web 88 and the inclination of the lower end of the armature 98b away from the web 88 allow the armature 98 to pivot so that extension 101 can drive the trip bar 70 counterclockwise away from the secondary latch 61 when the armature end 98b is attracted to the lower pole face 94b. 1

Electrical currentflows through the bimetal 24 when the breaker is closed and generates a magnetic field through the pole piece 86 both above and below the arms '92 i.e. magnetic lines of force pass through the upper 94a and lower 94b pole faces to the corresponding parts of the armature 98. In order to move the lower end of the armature 98b toward the pole piece 86 it is necessary for the field generated in the lower pole piece 94b to overcome not only the resilient biasing of the spring 102 but also the magnetic forces generated between the upper armature 98a and upper pole piece 94a. To control the attractive effort of the upper pole piece 94a on the armature and thereby control the trip point of the device means are provided for producing an adjustable gap between the parts i.e. between the upper armature 98a and the upper pole piece 94a. This is accomplished by means of an adjusting screw 104 which bears against the lower end of the armature 98b and determines its rest position. When the screw 104 is driven, viewed in FIG. 1, through case-mounted plate 106, toward the bimetal 24 the inclination of the upper armature end 98a with respect to the pole face 94a is changed to produce a separation or gap therebetween. This gap results in a lessening of the attractive force at this point and is there-fore usable for calibrating the magnetic or instantaneous tripping point of the breaker.

The pole piece 86 of each pole is protected from accidental contact with the current-carrying flexible braid 22 by means of an insulating barrier 108.

The circuit breaker is illustrated in FIG. 1 in its open condition, with the cradle 46 latched so that the mechanism is in condition for driving the contacts closed when operated. This is accomplished by moving manual lever 40 to the right in the drawings. The upper ends of tension springs 60 are correspondingly shifted to the right in over-travel spring or springs 34 (in the case of multiple poles).

When the contacts have been closed in this manner, the line of upward thrust through the knee 54 passes to the right of the upper toggle pivot 56 in the cradle 46. In the event of an over-current, cradle 46 is released for clockwise swing about its pivot 48, and the upper toggle pivot 56 shifts to the right and across the resulting line of action of the springs 60. When this takes place, the tensioned over-center springs 60 are free to cause sudden collapse of the toggle and correspondingly, to lift the various contact carriers 32 as a unit from their closed position.

The operation of the secondary latch 61 which engages and restrains the cradle 46 is in turn controlled by the overcurrent sensing means 80. In the event of a sustained overcurrent condition the bimetal 24 is heated and caused to deflect to the left as viewed in FIG. 1. Upon the occurrence of a suflicient overcurrent for the prescribed period of time the bimetal is deflected until it drives against the screw 84 carried by the trip bar 70. It should be noted that there is no load at all imposed on the bimetal until it engages the screw 84. The trip bar 70 retains the secondary latch 61 in position because of the spring 72 and because the biasing component of force due to the point of application of the force by the end 74 of the secondary latch 61 to the primary latch 77 on which it rests is toward the secondary latch. Therefore only a minimal load on the bimetal 24 is produced by the forces retaining the trip bar in position beneath the secondary latch 61. When the trip bar has been deflected beyond the point of engagement of primary latch surface 75 with the secondary latch end 74, the secondary latch is released and moves toward its tripped position about its pivot 63 to release the cradle 46. The trip bar is driven clear of the secondary latch by the secondary latch arm 64.

The latch 61 is swung about its pivot in the cradle releasing direction by the clockwise component of force of the cradle until the stop 68 engages the frame 44. When the bimetal 24 is cool the trip bar may be reset to its position beneath the secondary latch end 74. Driving the manual lever 40 toward the off position as shown in FIG. 1 from its center tripped position causes the end 47 of the cradle 46 to engage the tail 66 of the secondary latch 61 and drive it from its maximum tripped position about its pivot 63 until the trip bar 70, urged thereto by 'the spring 72, is returned beneath the arm 64 of the secondary latch 61. The configuration of the secondary latch arm 64 guides the trip bar 70 clockwise to a nonfor rotation about its pivots similar to that caused by the operation of the bimetal 24. The amount of current operable to trip the armature 98 is determined by the ratio of upper to lower armature attractive forces developed in their respective sections of the armature and pole pieces. This ratio is adjusted by the screw 104 which bears against the lower armature 98b. This screw varies the gap between the upper armature 98a and upper pole faces 94a in the rest or no current condition. The

greater the gap therebetween the less force required on the lower armature '98a to cause the pivotal action required for tripping the breaker. Since the armature bridges the legs 90 of the pole pieces 86 the magnetic circuit through the armature 98 is concentrated therein, being varied in intensity by the respective air gaps between the upper and lower armature-98a, 98b and their 6 respective segments of the pole piece 94a, 94b. When the lower armature 98b begins to move toward the pole piece 86 the gap between the upper armature 98a and the pole piece is increased proportionally. The attractive force on the upper armature is limited by the magnetic saturation of the parts. Once saturation has been reached, a further increase in current does not increase the field strength. However, since the lower armature is larger, an increase in current beyond that which causes saturation of the upper armature does cause an increase in the attraction of the lower armature to the pole piece. The forces become unbalanced and the armature begins to pivot. The movement of the lower armature toward the pole piece produces a slight increase in the gap and results in a decrease in the hol-dback force on the armature 98a and the lower armature 98b. The lower armature closes to the pole piece 86 with a snap action when the attractive force on the lower armature is greater than the attractive force on the upper armature combined with the force of spring 102. The tripping range of the above described magnetic trip may be varied over a wide range with the same spring 102 biasing the upper armature toward the pole piece. A magnetic tripping range variable from 100 amperes to 1100 amperes has been achieved by varying the gap between the upper armature and the pole piece. With a slightly stronger spring 102 the upper end of the range has been extended to 2000 amperes with the same pole piece-and-armature structure.

The bimetal 24 and the armature 98 have a common plane of action with armature interposed between the bimetal 24 and the trip bar 70. The trip bar contacting end 101 of the armature is located beneath and in line with the bimetal calibrating screw 84 on the trip bar 70. This construction provides a compact overcurrent sensing means which is readily assembled. As an additional feature the armature 98 is bodily shiftable along the arms 02 toward the stops 96 by the bimetal 24 in the event that overtravel of the bimetal should occur beyond the tripping point due to the heat built up in the bimetal. The bimetal then engages the armature 98 above its pivot 99. This is an important feature since it protects the bimetal against developing a set or distortion which would upset the calibration of the breaker as would be the case if the bimetal was urged against fixed or rigid stop while heated.

While only one embodiment of the invention has been shown and described it will be readily apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention.

What I claim is:

1. A circuit breaker having a pair of separable contacts and operating means for opening and closing said contacts, and current-responsive means for causing automatic opening of the contacts, said current-responsive means including a trip member, an elongated current carrying member connected electrically in series with said contacts, an elongated U-shaped core surrounding said current carrying member and extending therealong for substantially the entire length of said member, an armature having one long portion and one short portion rigidly interconnected, said armature being pivotally mounted on said core between said long and short portions, means resiliently urging said short portion against said core, said armature and said core being shaped so that, when said short portion is against said core, there is a substantial air gap between said core and said long armature portion, and an operative connection from said armature to said trip member for effecting automatic opening of the circuit breaker in response to overload current through said current carrying member. I

2. A circuit breaker having a pair of separable contacts and operating means for opening and closing said contacts, and current-responsive means for causing automatic opening of the contacts, said current-responsive means including a trip member, an elongated current carrying bimetal fixed at one end and adapted to engage said trip member at the other end for eflecting automatic opening of the contacts in response to moderate sustained overload currents through the bimetal, an elongated U-shaped core surrounding said bimetal and extending therealong for substantially the entire length of said bimetal, an armature having one long portion and one short portion rigidly interconnected, said armature being pivotally mounted on said core between said long and short portions adjacent the free end of the bimetal, means resiliently urging said short portion against said core, said armature and said core being shaped so that, when said short portion is against said core, there is a substantial air gap between said core and said long armature portion, and an operative connection from said armature to said trip memberfor effecting automatic opening of the circuit breaker in re sponse to severe overload currents.

3. A circuit breaker having a pair of separable contacts and operating means for opening and closing said contacts, and current-responsive means for causing automatic opening of the contacts, said current-responsive means including a trip member, an elongated current carrying bimetal fixed at one end and adapted to engage said trip member at the other end for effecting automatic opening of the contacts in response to moderate sustained overload currents through the bimetal, an elongated U-shaped core surrounding said bimetal and extending therealong for substantially the entire length of said bimetal, an armature having one long portion and one short portion rigidly interconnected, said armature being pivotally mounted on said core between said long and short portions adjacent the free end of the bimetal, means resiliently urging said short portion against said core, said armature and said core being shaped so that, when said short portion is against said core, there is a substantial air gap between said core and said long armature portion, means for selectively'setting said gap, and an operative connection from said armature to said trip member for effecting automatic opening of the circuit breaker in response to severe overload currents.

4. A circuit breaker having a pair of separable contacts and operating means for opening and closing said contacts, and current-responsive means for causing automatic opening of the contacts, said current-responsive means including a releasable member, said current-responsive means having a magnetic core formed as an elongated channel having a web portion and lateral upstanding poles, an elongated armature disposed along the core and across the poles, said armature having a pivotal mounting transverse to the length of the armature and disposed to divide the armature into short and long portions at opposite sides of the transverse pivotal mounting, the armature and the poles being shaped so as to form a relatively large air gap between said long armature portion and said poles and to form a substantially smaller air gap between said short armature portion and said poles in the normal position of the armature, a spring biasing said armature to said normal position, an elongated conductor connected electrically in series with said contacts and physically interposed between and extending along said armature and core, and a mechanical control connection from said armature to said releasable member to effect automatic opening of the contacts by said armature in response to overload currents.

5. A circuit breaker having a pair of separable contacts and operating means for opening and closing said contacts, and current-responsive means for causing automatic opening of the contacts, said current-responsive means including a releasable member, said current-responsive means having a magnetic core formed as an elongated channel having a web portion and lateral upstanding poles, an elongated armature disposed along the core and across the poles, said armature having a pivotal mounting transverse to the length of the armature and disposed to divide the armature into short and long portions at opposite sides of the transverse pivotal mounting, the armature and the poles being shaped so as to form a relatively large air gap between said long armature portion and said poles and to form a substantially smaller air gap between said short armature portion and said poles in the normal position of the armature, means for selectably setting the air gaps between said armature portions and said poles in said normal position, a spring biasing said armature to said normal position, an elongated conductor connected electrically in series with said contacts and physically interposed between and extending along said armature and core, and a mechanical control connection from said armature to said releasable member to eifect automatic opening of the contacts by said armature in response to overload currents.

6. A circuit breaker having a pairof separable contacts and operating means for opening and closing said contacts, and current-responsive means for causing automatic opening of the contacts, said current-responsive means including a releasable member, said current-responsive means having a magnetic core formed as an elongated channel having a web portion and lateral upstanding poles, an elongated armature disposed along the core and across the poles, said armature having a pivotal mounting transverse to the length of the armature and disposed to divide the armature into short and long portions at opposite sides of the transverse pivotal mounting, the armature and the poles being shaped so as to form a relatively large air gap between said long armature portion and said poles and to form a substantially smaller air gap between said short armature portion and said poles in the normal position of the armature, means for selectably setting the air gaps between said armature portions and said poles in said normal position, a spring biasing said armature to said normal position, an elongated current carrying bimetal connected electrically in series with said contacts and physically interposed between and extending along said armature and core, and a mechanical control connection from said armature and from said bimetal to said releasable member to efiect automatic opening of the contacts by said armature and said bimetal in response to overload currents.

7. A circuit breaker having a pair of separable contacts and operating means for opening and closing said contacts and current-responsive means including a trip member for causing automatic opening of the contacts, said current-responsive means including an elongated U- shaped core, an armature having one long portion and one short portion rigidly connected together, said armature being pivotally mounted between said long and short portions and being shaped in relation to said core so that said long portion and said short portion of the armature have relatively large and small air gaps respectively, means resiliently urging said short portion against said core, an elongated current carrying member electrically connected in series with said separable contacts and physically disposed along and interposed between said armature and said elongated core, said armature having an operative connection to said trip member for effecting automatic opening of the circuit breaker in response to overload currents.

8. A circuit breaker having a pair of separable contacts and operating means for opening and closing said contacts and current-responsive means including a trip member for causing automatic opening of the contacts, said current-responsive means including an elongated U- shaped core, an armature having one long portion and one short portion rigidly connected together, said armature being pivotally mounted between said long and short portions and being shaped in relation to said core so that said long portion and'said short portion of the armature have relatively large and small air gaps, respectively, an

elongated current carrying bimetal electrically connected 'in series with said separable contacts and physically disposed along and interposed between said armature and 9 said elongated core, said bimetal and said armature both having operative connections to said trip member for effecting automatic opening of the circuit breaker in re sponse to moderate, sustained overload currents and in response to severe overload currents, respectively.

9. A circuit breaker having a pair of separable contacts and operating means for opening and closing said contacts and current-responsive means including a trip member for causing automatic opening of the contacts, said current-responsive means including an elongated U- shaped core, an armature having one'long portion and one short portion rigidly connected together, said armature being pivotally mounted between said long and short portions and being shaped in relation to said core so that said long portion and said short portion of the armature have relatively large and small air gaps, respectively, means for selectively setting said air gaps between said armature portions and said poles, an elongated current carrying bimetal electrically connected in series with said separable contacts and physically disposed along and interposed between said armature and said elongated core, said bimetal and said armature both having operative connections to said trip member for effecting automatic opening of the circuit breaker in response to moderate, sustained overload currents and in response to severe overload currents, respectively.

10. A multi-pole molded case circuit breaker having a pair of separable contacts per pole, a frame mounted in said case, operating means for opening and closing said contacts, said operating means mounted on said frame, said operating means including a releasable member to effect opening of said contacts, and overcurrent responsive means for releasing said member, said overcurrent responsive means including a multi-pole trip bar pivotally mounted on said frame, a latch pivotally mounted on said frame, said latch being interposed between and operatively connected to said trip bar and said releasable member, and individual overcurrent sensing elements in each pole for operating said trip bar.

11. A multi-pole molded case circuit breaker having a pair of'separable contacts per pole, a frame mounted in said case, operating means for opening and closing said contacts, said operating means mounted on said frame, said operating means including a releasable member to efiect opening of said contacts, and overcurrent responsive means for releasing said member, said overcurrent responsive means including a multi-pole trip bar pivotally mounted on said frame, a latch pivotally mounted on said frame, said latch restraining said releasable member, said latch being retained in said restraining position by said trip bar, and individual overcurrent sensing elements in each pole for operating said trip bar.

12. A multi-pole molded case circuit breaker having a pair of separable contacts per pole, a frame mounted in said case, operating means for opening and closing said contacts, said operating means mounted on said frame, said operating means including a releasable member to effect opening of said contacts, and overcurrent responsive means for releasing said member, said overcurrent responsive means including a multi-pole trip bar pivotally mounted on said frame, a latch pivotally mounted on said frame, said latch restraining said releasablemember, said latch having a portion engaging said trip bar whereby said latch is retained in position, the configuration of said latch and said trip barat their point of mutual engagement providing a reaction point for the force on said latch, said reaction force having its major component acting through the pivot of said trip bar on said frame and a minor component biasing said trip bar into engagement with said latch, and individual overcurrent sensing elements in each pole for operating said trip bar.

13. A multi-pole molded case circuit breaker having a pair of separable contacts per pole, a frame mounted in said case, operating means for opening and closing said contacts, said operating means mounted on said frame,

said operating means including a releasable member to effect opening of said contacts, and overcurrent responsive means for releasing said member, said overcurrent responsive means including a multi-pole trip bar pivotally mounted on said frame, a primary latch secured to said trip bar, a secondary latch pivotally mounted on said frame, said secondary latch restraining said releasable member, said secondary latch being retained in said restraining position by engagement with said primary latch, and individual overcurrent sensing elements in each pole for operating said trip bar.

14. A circuit breaker according to claim 13 wherein said primary latch is a bimetallic ambient temperature compensator.

15. A circuit breaker having a pair of separable contacts and operating means for opening and closing said contacts and current-responsive means including a trip member for causing automatic opening of the contacts, said current-responsive means including an elongated U- shaped core, an armature having one long portion and one short portion rigidly connected together, said armature being pivotally mounted between said long and short portions and being shaped in relation to said core so that said long portion and said short portion of the armature have relatively large and small air gaps, respectively, said armature abutting said core in a first position, said armature being shiftable away from said core to a displaced position, an elongated current carrying bimetal electrically connected in series with said separable contacts and physically disposed along and interposed between said armature and said elongated core, said bimetal and said armature both having operative connections to said trip member for effecting automatic opening of the circuit breaker in response to moderate, sustained overload currents and in response to severe overload currents, respectively, said armature being shiftable from said first position to said displaced position by said bimetal.

16. A circuit breaker having a pair of separable contacts and operating means for opening and closing said contacts, and current-responsive means for causing automatic opening of the contacts, said current-responsive means including releasable member, said current-responsive means having a magnetic core formed as an elongated channel having a web portion and laterally upstanding poles, an elongated armature disposed along the core and across the poles, said armature having a pivotal mounting transverse to the length of the armature, said armature abutting said core in a first position, said armature being shiftable away from said core to a displaced position, said pivotal mounting being disposed to divide the armature into short and long portions at opposite sides of the transverse pivotal mounting, the armature and the poles being shaped so as to form a relatively large air gap between said long armature portion and said poles and to form a substantially smaller air gap between said short armature portion and said poles in the first position of the armature, means for selectably setting the air gaps between said armature portions and said poles in said first position, a spring biasing said armature to said first position, an elongated current-carrying bimetal connected electrically in series with said contacts and physically interposed between and extending along said armature and core, and a mechanical control connection from said armature and from said bimetal to said releasable member to effect automatic opening of the contacts by said armature and said bimetal in response to overload currents, said armature being shiftable from said first position to said displaced position by said bimetal against the bias of said spring.

17. A multi-pole molded case circuit breaker having a pair of separable contacts per pole, a frame mounted in said case, operating means for opening and closing said contacts, said operating means mounted on said frame, said operating means including a releasable member to effect opening of said contacts, and overcurrent responsive means for releasing said member, said overcurrent responsive means including a multi-pole trip bar pivotally mounted on said frame, a latch pivotally mounted on said frame, said latch restraining said releasable member, said latch being retained in said restraining position by said trip bar, said latch and said trip bar having mutuallyengaging portions that limit the latch-trip bar engagement, and individual overcurrent sensing elements in each pole for operating said trip bar.

18. A multi-pole molded case circuit breaker having a pair of separable contacts per pole, a frame mounted in said case, operating means for opening and closing said contacts, said operating means mounted on said frame, said operating means including a releasable member to effect opening of said contacts, and overcurrent responsive means for releasing said member, said overcurrent responsive means including a multi-pole trip bar pivotally mounted on said frame, a primary latch secured at one end to said trip bar and having a free end extending therefrom, a secondary latch pivotally mounted on said frame,

said secondary latch restraining said releasable member, said secondary latch being retained in said restraining position by engagement with said primary latch, said secondary latch having a surface for engaging the free end of said primary latch so as to limit the extent of the secondary latch-primary latch engagement, and individual overcurrent sensing elements in each pole for operating said trip bar.

References Cited by the Examiner UNITED STATES PATENTS 2,047,739 7/36 Lingal 20088 2,328,458 8/43 Jackson et a1. 20088 2,494,761 1/50 Jackson et a1. 20088 2,889,428 6/59 Kingdon et a1 20088 2,902,560 9/59 Stanback et a1. 20088 BERNARD A. GILHEANY, Primary Examiner.

20 ROBERT K. SCHAEFER, Examiner.

Disclaimer 3,209,098.-Henry S. Wingard, Cranford, NJ. CIRCUIT BREAKERS HAVING IMPROVED TRIPPING MECHANISMS. Patent dated Se t. 28, 1965. Disclaimer filed June 30, 1966, by the assignee, Federal aeifie Electric Oompcmy.

Hereby enters this disclaimer to claims 10, 11 and 13 of said patent.

[Ofiieial Gazette September 13, 1.966.] 

10. A MULTI-POLE MOLDED CASE CIRCUIT BREAKER HAVING A PAIR OF SEPARABLE CONTACTS PER POLE, A FRAME MOUNTED IN SAID CASE, OPERATING MEANS FOR OPENING AND CLOSING SAID CONTACTS, SAID OPERATING MEANS MOUNTED ON SAID FRAME, SAID OPERATING MEANS INCLUDING A RELEASABLE MEMBER TO EFFECT OPENIGN OF SAIDCONTACTS, AND OVERCURRENT RESPONSIVE MEANS FOR RELEASING SAID MEMBR, SAID OVERCURRENT RESPONSIVE MEANS INCLUDING A MULTI-POLE TRIP BAR PIVOTALLY MOUNTED ON SAID FRAME, A LATCH PIVOTALLY MOUNTED ON SAID FRAME, SAID LATCH BEING INTERPOSED BETWEEN AND OPERATIVELY CONNECTED TO SAID TRIP BAR AND SAID RELEASABLE MEMBER, AND INDIVIDUAL OVERCURRENT SENSING ELEMENTS IN EACH POLE FOR OPERATING SAID TRIP BAR. 